Mosiah 18:29

And this he said unto them, having been commanded of God; and they did walk uprightly before God, imparting to one another, both temporally and spiritually, according to their needs and their wants.

He told them this because God had commanded him. They lived right before God. They shared with each other, both physical things and spiritual things. They shared based on what people needed and wanted.

This is what he taught them, because God had commanded it. And they lived right before God, sharing with each other—both their material goods and their spiritual strength—according to what each person needed.